Image pickup device, radiation image pickup device and image processing system

ABSTRACT

An image pickup device has a plurality of photoelectric converter substrates carrying respective input/output terminals connected to the photoelectric converters. The device comprises leads connected to the input/output terminals and extending to the side opposite to the light receiving surfaces of the photoelectric converter substrates thorough the gaps separating the substrates.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of application Ser. No. 09/900,035, filedJul. 9, 2001 now U.S. Pat. No. 6,800,836, the entire content of which ishereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an image pickup device, a radiation imagepickup device and an image processing system. More particularly, thepresent invention relates to a radiation image pickup device adapted toextend the image pickup area and an image processing system using such aradiation image pickup device. For the purpose of the invention,radiation refers to α rays, β rays, γ rays and so on and includesX-rays.

2. Related Background Art

A film screen system realized by combining intensifying screens and anX-ray film is popularly used for X-ray photography for the purpose ofmedical diagnosis. With such a system, the X-rays transmitted through anobject to be photographed contain information on the inside of theobject and are converted into rays of visible light showing intensitiesproportional to those of the transmitted X-rays by the intensifyingscreens. Then, the X-ray film is exposed to the rays of visible light.

In recent years, X-ray digital image pickup devices have been marketed.With such X-ray digital image pickup devices, X-rays are converted intorays of visible light with intensities proportional to those of theoriginal X-rays by means of a scintillator and then the obtained rays ofvisible light are converted into an electric signal by means of aphotoelectric converter, which electric signal is then transformed intoa digital signal by means of an A/D converter.

More specifically, a known type of X-ray digital image pickup devicecomprises an ordinary image pickup device formed by arranging elementson a glass substrate, each element having an amorphous semiconductorsandwiched between a pair of electrodes, and a scintillator laid on theimage pickup device in order to convert X-rays into rays of visiblelight. Another known type of X-ray digital image pickup device isrealized by two-dimensionally linking modules, each comprising a taperedoptical fiber formed by heating and softening a bundle of optical fibersand drawing the softened bundle, a photoelectric converter such as a CCDarranged at the tapered side of the optical fiber and a scintillatorlaid on the opposite side of the optical fiber.

X-ray digital image pickup devices of the above described types aremostly used for medical diagnosis and other applications. Such a deviceis required to show a high resolution, a low noise level, an ability ofproducing moving images and a wide imaging angle so that the doctor maybe able to detect the diseased area quickly and make an accuratediagnosis.

However, while X-ray digital image pickup devices comprising amorphoussemiconductors typically made of silicon and arranged on a glasssubstrate are adapted to show a large sensor effective area, they areaccompanied by problems including that the size of pixels cannot bereduced because of the manufacturing process and the devicecharacteristics and that the device sensitivity is limited. Therefore,devices of this type are not adapted to high speed operationparticularly in terms of displaying moving images.

On the other hand, X-ray digital image pickup devices comprisingphotoelectric converters such as CCDs realized by using a siliconsubstrate have a problem that they cannot show a large sensor effectivearea mainly because of the restrictions in the manufacturing process andthe high power consumption level that produces heat, although they areadapted to realize a small pixel size and pick up moving images becausethey are highly sensitive and can be driven at high speed.

There has been proposed a device comprising an increased number ofelements, using optical fibers tapered in such a way that non-sensorareas of the photoelectric converters may not overlap in order to makeit show an enlarged sensor effective area. FIG. 1 of the accompanyingdrawings is a schematic illustration of some of the photoelectricconverters of such a device. In FIG. 1, there are shown substrates 1carrying respective photoelectric converters, scintillators 3 forconverting X-rays into rays of visible light showing a wavelength thatcan be detected by the photoelectric converters, a base member 7,tapered optical fibers 8, protection glass plates 9 and bonding wires11. Reference numeral 12 in FIG. 1 denotes a ceramic package.

However, a tapered optical fiber is costly and the ratio of dimensionalreduction is not stable because the tapering process involvesdimensional dispersions. Furthermore, while several tapered opticalfibers that are thick and heavy may be linked together, it is notrealistic to link a large number of tapered optical fibers in order toproduce a sensor effective area necessary for imaging the chest of asubject. Additionally, tapered optical fibers show a poor lighttransmission factor to a great disadvantage of the device.

FIG. 2 of the accompanying drawings is a schematic illustration of aconventional X-ray moving image system using an image intensifier (I—I).In FIG. 2, reference numeral 16 denotes the I—I. The X-rays striking thelight entering surface are converted into electrons, which aremultiplied to realize a high sensitivity of the system. The electronsare then converted to rays of light at the light exiting surface to showan image, which is then input to a CCD camera 15.

However, a system comprising such an image intensifier (I—I) inevitablyshows large dimensions because it comprises a vacuum tube.

In the case of a CCD image pickup device, peripheral circuits andelectrodes are required to be located in areas outside the display pixelarea to inevitably make the peripheral marginal area surrounding theeffective display area large as shown in FIG. 3A of the accompanyingdrawings. Additionally, the X-ray image sensor itself faces a limit fordownsizing.

X-ray image sensors that are used for dental diagnosis are designed tobe put into the mouth of the patient in order to pick up an image of theinside of the mouth. Then, however, it is impossible to take a pictureof some of the molar teeth with such an X-ray image sensor.Particularly, it is highly difficult to put such an X-ray image sensorinto the mouth of a child and, if such a sensor is forced into themouth, it can induce a feeling of vomiting on the part of the patient tomake the effort for taking a picture abortive.

As described above, it has been highly difficult to realize an X-raydigital image pickup device for medical diagnosis that is adapted toshow a moving image with a high resolution if it is made to have a largesensor effective area and show reduced dimensions at low cost.

SUMMARY OF THE INVENTION

In view of the above identified circumstances, it is therefore theobject of the present invention to provide a radiation image pickupdevice such as an X-ray image pickup device for medical diagnosis thatis adapted to show a moving image with a high resolution and, at thesame time, can be made to have a large sensor effective area and showreduced dimensions at low cost and also an image processing system usingsuch a device. Such a radiation image pickup device minimizes the areathat can not be imaged (to efficiently exploit the effective area) whentaking an X-ray picture of the teeth of the patient and comprises adownsized X-ray image sensor that can also minimize the load of thepatient when it is put into the mouth.

According to the invention, the above object is achieved by providing aradiation image pickup device having a plurality of photoelectricconverters and a plurality of photoelectric converter substratescarrying respective terminals connected to the photoelectric converterson light receiving surfaces of the photoelectric converter substrates.The device further includes: (1) leads connected to the terminals andextending to a side opposite to the light receiving surfaces of thephotoelectric converter substrates through gaps between the substrates;and (2) a wavelength converter for wavelength-converting radiation and alight guide section for guiding light from the wavelength converter tothe plurality of photoelectric converters, the wavelength converter andthe light guide section being provided with the plurality ofphotoelectric converter substrates.

In another aspect of the invention, there is provided an image pickupdevice having a plurality of photoelectric converter substrates, eachcarrying a plurality of photoelectric converters, said device comprisinginput/output terminals connected respectively to said photoelectricconverters, said input/output terminals being arranged on surfaces ofsaid photoelectric converter substrates different from the surfacescarrying said photoelectric converters.

In still another aspect of the invention, there is provided a radiationimage pickup device comprising an image pickup device according to theinvention and a wavelength converter arranged at the side of the lightreceiving surfaces of said photoelectric converter substrates of theimage pickup device.

In still another aspect of the invention, there is provided an imageprocessing system comprising an image pickup device according to theinvention, image processing means for processing signals from the imagepickup device for an image, a recording means for recording the signalsfrom the image processing means, a display means for displaying signalsfrom the image processing means and electric transmission means fortransmitting signals from the image processing means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross sectional lateral view of a known radiationimage pickup device, showing a part thereof.

FIG. 2 is a schematic illustration of a known X-ray moving image systemcomprising an X-ray image intensifier (I—I).

FIG. 3A is a schematic plan view of a known CCD image pickup device.

FIG. 3B is a schematic lateral view of the known CCD image pickup deviceof FIG. 3A.

FIG. 4 is a schematic cross sectional lateral view of a first embodimentof image pickup device according to the invention, showing a partthereof.

FIG. 5 is a schematic perspective view of the embodiment of image pickupdevice of FIG. 4.

FIG. 6 is a schematic plan view of the embodiment of image pickup deviceof FIG. 4, showing a comer section thereof.

FIG. 7A is an enlarged schematic plan view of the embodiment of imagepickup device of FIG. 4, showing a part thereof where some of theinput/output terminals are bonded to one of the flexible wiringsubstrate 4.

FIG. 7B is an enlarged schematic lateral view corresponding to FIG. 7A.

FIG. 8 is a schematic illustration of the process of bending a lead 401and extending it to the rear side of one of the photoelectric convertersubstrates 1.

FIG. 9 is an enlarged schematic plan view of the embodiment of FIG. 4,showing a part thereof to illustrate the arrangement of pixels betweenphotoelectric converter substrates.

FIG. 10A is a schematic cross sectional lateral view of the embodimentof FIG. 4, showing a part thereof to illustrate how the light guide isbonded to the photoelectric converter substrates.

FIG. 10B is a schematic plan corresponding to FIG. 10A illustrating theadhesive filling step.

FIG. 11 is a schematic cross sectional lateral view of the embodiment ofFIG. 4, illustrating a different manufacturing step thereof.

FIG. 12 is a schematic cross sectional lateral view of a secondembodiment of image pickup device according to the invention.

FIG. 13 is an exploded schematic perspective view of the embodiment ofFIG. 12.

FIG. 14A is a schematic cross sectional lateral view of the embodimentof FIG. 12, illustrating a different manufacturing step thereof.

FIG. 14B is a schematic plan view of the base member of the embodimentof FIG. 12.

FIG. 15 is a schematic cross sectional lateral view of the embodiment ofFIG. 12, illustrating a further different manufacturing step thereof.

FIG. 16 is a schematic cross sectional lateral view of a thirdembodiment of image pickup device according to the invention.

FIG. 17 is an exploded schematic perspective view of the embodiment ofFIG. 16.

FIG. 18A is a schematic plan view of one of the photoelectric convertersubstrates 1 of the embodiment of FIG. 16.

FIG. 18B is a schematic cross sectional view corresponding to FIG. 18A.

FIGS. 19A, 19B, 19C and 19D are schematic cross sectional lateral viewsof the embodiment of FIG. 16, showing a part thereof to illustratedifferent manufacturing steps.

FIG. 20 is a schematic cross sectional lateral view of the embodiment ofFIG. 16, showing a different manufacturing step.

FIG. 21 is a schematic perspective view of a fourth embodiment of imagepickup device according to the invention.

FIG. 22A is a schematic cross sectional lateral view of the embodimentof FIG. 21.

FIG. 22B is a schematic cross sectional plan view of the embodiment ofFIG. 21.

FIGS. 23A, 23B, 23C, 23D and 23E are schematic views of the embodimentof FIG. 21, showing a part thereof to illustrate different manufacturingsteps.

FIG. 24 is a schematic illustration of a radiation image pickup systemthat can be realized by using an image pickup device according to theinvention.

FIG. 25 is a schematic conceptual illustration of an embodiment of imageprocessing system according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, the present invention will be described in greater detail byreferring to the accompanying drawings that illustrate preferredembodiments of the invention. While an image pickup device according tothe invention can suitably be used for a radiation image pickup device,the present invention is by no means limited thereto.

(First Embodiment)

FIG. 4 is a schematic cross sectional lateral view of the firstembodiment of image pickup device according to the invention, showing apart thereof. FIG. 5 is a schematic perspective view of the embodimentand schematically illustrates the photoelectric converter substrates 1of this embodiment.

Referring to FIGS. 4 and 5, the radiation irradiating an object producesinformation showing differences in the intensity thereof to reflect thestate of the inside of the object. Then, the wavelength of the radiationis converted into one that can be detected by the photoelectricconverters by the scintillator layer 3 operating as wavelengthconverter. The radiation is then made to pass through the light guidesection 2 and the adhesive layer 6 before being detected by thephotoelectric converter substrates 1 carrying a plurality ofphotoelectric converters 100 thereon. The detected information is thenled to the rear side of the photoelectric converter substrates 1 fromthe input/output circuits arranged on the photoelectric convertersubstrates 1 by way of bumps 5 and leads extending through the bondedgaps of the photoelectric converter substrates 1.

The leads are bent at the respective edges of the photoelectricconverter substrates 1 and extended to the side opposite to the onewhere the photoelectric converters 100 are arranged on the photoelectricconverter substrates 1.

The photoelectric converter substrates 1 are arranged side by side andbonded to a common light guide section 2 by means of the adhesive 6.With this arrangement, it is not necessary to lay wires on the surfacesof the photoelectric converter substrates 1 to transfer the electriccharges detected from the photoelectric converters 100 to a processingcircuit so that the imaging effective area of the embodiment can beincreased. In the case of a radiation detector, radiation may betransmitted through the scintillator 3, if slightly, and hence the wiresextending to the rear side of the substrates of the embodiment serve forprotection against radiation. The protection effect of this arrangementis particularly effective when the photoelectric converter substrates 1are made of a material that blocks or absorbs radiation.

FIG. 5 is a schematic perspective view of this embodiment of imagepickup device. Referring to FIG. 5, the photoelectric convertersubstrates 1 are arranged two-dimensionally in three rows and threecolumns and leads and flexible circuit substrates 4 are extending fromthe bonded gaps of the photoelectric converter substrates 1 to the rearside relative to the light guide section 2. FIG. 6 is a schematic planview of this embodiment of image pickup device, showing a comer sectionof one of the photoelectric converter substrates 1 made of silicon.Referring to FIG. 6, the photoelectric converter substrate 1 carriesthereon two-dimensionally arranged light receiving pixels (photoelectricconverters) 100, external input/output terminals 103, a vertical drivecircuit for sequentially driving the two-dimensionally arranged pixels100, a column scanning circuit 102 and wires 104 connecting thecircuits, the pixels and the electrode terminals. CMOSs mayadvantageously be used for the photoelectric converters.

The light receiving pixels 100 are arranged substantially over theentire surface of the photoelectric converter substrate 1 at a pitch of100 μm. The input/output terminals 103 are arranged in a distributedmanner at regular intervals along an edge of the photoelectric convertersubstrate 1. Protection circuits 115 are arranged between theinput/output terminals of the photoelectric converters 100 and theprocessing circuit to protect the circuits against electrostaticdestruction and other damages.

While each of the light receiving pixels 100 arranged along the drivecircuit 102 and the input/output terminals 103 that are distributed andalso along the edges of the light receiving pixels 100 has a lightreceiving area smaller than any of the remaining light receiving pixelsand hence may receive light at a lower rate if compared with the latter,its output may be corrected to make it balanced with the output of anyother light receiving pixel.

FIGS. 7A and 7B schematically illustrate a part of the embodiment wherethe leads 401 of a flexible wiring substrate 4 are bonded to therespective input/output terminals 103 arranged on the surface of aphotoelectric converter substrate 1 that carries photoelectricconverters 100. FIG. 7A is a schematic plan view of the part, whereasFIG. 7B is a schematic cross sectional view thereof.

Referring to FIGS. 7A and 7B, firstly bumps 5 are formed on therespective input/output terminals 103 arranged on the photoelectricconverter substrate 1. The bumps 5 may be of the so-called stud bumptype or formed by plating. The leads 401 of the flexible wiringsubstrates 4 are formed by etching copper foil and plated with nickel orgold.

Each of the bumps 5 on the input/output terminals 103 is connected to acorresponding lead 401 of a flexible wiring substrate 4 typically by ametal bonding method using ultrasonic waves. Then, the bonded lead 401of the flexible wiring substrate 4 is bent at the corresponding edge ofthe photoelectric converter substrate 1.

FIG. 8 is a schematic illustration of the process of bending a lead 401and extending it to the rear side of the photoelectric convertersubstrate 1. The photoelectric converter substrate 1 connecting the lead401 of the flexible wiring substrate 4 to the related light receivingpixels 100 by way of the bump 5 is rigidly held to a table 17 typicallyby means of vacuum suction and its input/output terminal bonding sectionis lightly held by a holder member 18. Then, jig 19 is movedhorizontally to bend the lead by about 90 degrees.

In this embodiment, an organic insulating layer 105 (polyimide resinlayer) is formed on an area extending from the input/output terminal 103to the edge of the photoelectric converter substrate 1 in order toprevent any electric short circuiting that can occur as the edge of thephotoelectric converter substrate 1 contacts the lead 401 and/or anymechanical damage of the edge of the photoelectric converter substrate 1due to mechanical force from taking place when the lead 401 is bent. Anypossible short circuiting between the corresponding lateral side of thephotoelectric converter substrate 1 and the lead 401 can be prevented byarranging an insulating layer (polyimide layer) on the rear surface ofthe flexible wiring substrate 4. The polyimide layer has a thickness of25 μm and covered by an about 18 μm thick copper foil wiring layerformed by plating. Thus, the flexible wiring substrate 4 shows a totalthickness of about 43 μm without any adhesive applied thereto.

Then, as shown in FIGS. 4 and 5, the plurality of photoelectricconverter substrates 1 connected to the flexible wiring substrates 4carrying the bent leads 401 are bonded to the light guide section 2 bymeans of a transparent adhesive agent 6.

FIG. 9 is an enlarged schematic plan view of the embodiment, showing apart thereof to illustrate the arrangement of pixels between a pair ofphotoelectric converter substrates. If the pixels are arranged at apitch of 100 μm, any two adjacently located photoelectric convertersubstrates are arranged with a gap of 80 μm separating them, taking thethickness of each flexible wiring substrate 4 and the bonding accuracyinto consideration. Therefore, while the pixels there show irregularpitches of 100-80-140-80-100 as shown in FIG. 9, the defect of theirregularity is not visually remarkable and the quality of the producedimage is not particularly bad if compared with an arrangement that isdevoid of an entire row of pixels there.

The adhesive 6 preferably transmits light very well and shows anexcellent elasticity.

FIG. 10A is a schematic cross sectional lateral view of the embodiment,showing a part thereof to illustrate how the light guide section 2 isbonded to the photoelectric converter substrates 1. After applyingadhesive 15 at the four comers of each of the photoelectric convertersubstrates 1 for temporary bonding, the photoelectric convertersubstrate 1 is aligned with the predetermined position of the lightguide section 2 and then the adhesive 15 for temporary bonding ishardened. After bonding and aligning all the photoelectric convertersubstrates 1 in this way, the gaps separating the photoelectricconverter substrates and the gaps between the edges of the photoelectricconverter substrates 1 arranged along the outer periphery and thecorresponding edges of the light guide section 2 are sealed by a meansof a high viscosity adhesive 16.

However, one of the peripheral edges is not sealed and an opening 14 isleft there. Thereafter, the gap between the light guide section 2 andthe corresponding photoelectric converter substrates 1 at the opening 14is put into a vacuum condition in a vacuum chamber and the opening 14 isbrought into contact with a boat containing adhesive 6 therein asillustrated in FIG. 10B. Then, the vacuum condition is eliminated tomake the atmospheric pressure prevail there once again. As a result ofthe pressure difference, the adhesive 6 is drawn in to fill the gap. Theadhesive 6 and the adhesive 15 (shown in FIG. 10A) for temporary bondingare preferably made of a same material or different materials whoserefractive indexes are same or equivalent. With this process ofproviding a predetermined gap between the photoelectric convertersubstrates 1 and the light guide section 2 in advance by means of anadhesive 15 (shown in FIG. 10A) for temporary bonding and subsequentlybonding the photoelectric converter substrates 1 and the light guidesection 2, the plurality of photoelectric converter substrates can bealigned highly accurately.

Subsequently, the filling adhesive 6 is caused to harden and each of theflexible wiring substrates 4 extending from the photoelectric convertersis connected to related electronic parts 71 including the processingcircuit on the corresponding base member 7 as shown in FIG. 11. Whilethis embodiment comprises additional base members 7, the processingcircuits and other parts may be formed directly on the rear surfaces ofthe photoelectric converter substrates 1 to further reduce the height ofthe embodiment by selecting an appropriate material for thephotoelectric converter substrates 1.

The light guide section 2 may preferably be formed by using an opticalfiber plate that is formed by cutting a large bundle of optical fibersto make it show a plate-like profile. An optical fiber plate can beprepared through a process that is by far simpler than the process forpreparing a tapered bundle of optical fibers. While an optical fiberplate is preferably used for the light guide section in order to guidelight to the photoelectric converters without scattering it, a lighttransmitting substrate such as a glass substrate may alternatively beused for the light guide section when scattering of light is permissibleor expected to take place only scarcely.

When the embodiment is used as radiation image pickup device, the use ofa light guide member that is transparent relative to visible light butopaque relative to radiation between the scintillator for changing thewavelength of radiation and the photoelectric converters can effectivelyprevent any degradation and operation errors that can occur when thephotoelectric converters are exposed to radiation from taking place.When the light guide member is made of a material containing lead, theX-rays that are not converted to rays of visible light by thescintillator may be effectively blocked by the lead contained in thelight guide member to consequently minimize the adverse effect of X-rayson the photoelectric converters and produce X-ray images with littlenoise. While the embodiment is made to comprise a light guide member, itmay not necessarily comprise such a member. The scintillator 3 may bemade of gadolinium sulfide (GdS) or cesium iodide (CsI). An image pickupdevice that does not comprise a scintillator 3 may be used as aphotodetector for detecting rays of the visible light band.

(Second Embodiment)

FIG. 12 is a schematic cross sectional lateral view of a secondembodiment of image pickup device according to the invention. In FIG.12, the components that are same as or similar to those of the firstembodiment are denoted respectively by the same reference symbols andwill not be described any further. This embodiment differs from thefirst embodiment in that the base member of this embodiment is providedwith slits and bonded to the corresponding photoelectric convertersubstrates 1 by means of adhesive 8.

Each of the leads connected to the respective input/output terminals 103of the photoelectric converters 100 arranged on the photoelectricconverter substrates 1 by way of the bumps 5 is bent at thecorresponding edge of the related photoelectric converter substrate 1and extended to the rear surface side of the photoelectric convertersubstrate 1. Then, the photosensitive converter substrate 1 carrying aplurality of photoelectric converters 100 thereon is bonded to the basemember 7 by means of adhesive 8. The base member 7 is provided withslits 70 for allowing the leads and the flexible circuit substrates 4connected to the leads to pass therethrough and get to the rear side ofthe base member 7.

The radiation irradiating the object produces information showingdifferences in the intensity thereof to reflect the state of the insideof the object. Then, the information is expressed in terms ofdifferences in the intensity of rays of visible light by thescintillator 3 and then in terms of differences in the intensity of anelectric signal at the photoelectric converter substrates 1. Theelectric signal is then subjected to A/D conversion by a processingcircuit (not shown) arranged at the base member 7 and the original imageis restored by the image processing system that processes the signalproduced as a result of the A/D conversion.

FIG. 13 is an exploded schematic perspective view of the secondembodiment, which is a radiation image pickup device. A plurality ofphotoelectric converter substrates 1 are arranged two-dimensionally onthe base member 7 provided with slits 70 and a scintillator 3 isarranged thereon.

FIG. 14A is a schematic cross sectional lateral view of this embodiment,illustrating a manufacturing step where the photoelectric convertersubstrates 1 are bonded to the base member 7. The photoelectricconverter substrates 1 are aligned on a securing stage 20 for rigidlysecuring the photoelectric converter substrates 1 and subsequentlysucked and secured to the stage by way of vacuum holes arranged therein.The photoelectric converter substrates 1 can be aligned properly byusing transparent members arranged in necessary areas of the stage 20and using alignment marks formed respectively in the photoelectricconverters.

Then, a necessary amount of adhesive 8 is applied to the rear surface ofeach of the photoelectric converter substrates 1 and the adhesive iscaused to harden, while pressing the base member 7 provided with slits70 against the photoelectric converter substrates 1. More specifically,silicone resin of a wet-hardening type may be used for the adhesive 8.The adhesive 8 is not required to transmit light because it is appliedto the rear surfaces of the light receiving elements of the embodiment.FIG. 14B is a schematic plan view of the base member of this embodiment.As seen from FIG. 14B, the base member 7 is provided with a plurality ofslits 70 that are arranged to correspond to the flexible circuitsubstrates 4 extending respectively from the related edges of thephotoelectric converter substrates 1.

Then, as shown in FIG. 15, each of the flexible wiring substrates 4extending through the slits 70 is connected to related electronic parts71 including the processing circuits provided on the rear surface of thebase member 7.

A printed wiring substrate typically made of glass epoxy may be used forthe base member 7. Alternatively, a ceramic substrate or a glasssubstrate may be used for the base member 7. The substrate may contain asubstance such as Pb that can effectively block radiation and protectthe electronic parts 71 from the radiation, if slight, that has beentransmitted through the scintillator 3. Since the base member 7 needs tobe provided with slits 70 as shown in FIG. 14B, it is preferably suchthat the slits can be formed therethrough with ease. Preferably it islightweight and can mount electronic parts without difficulty.Therefore, it is preferably made of glass or ceramic in order to meetthose requirements. As in the first embodiment, a light guide sectionmay be arranged on the photoelectric converter substrates 1 of thisembodiment.

(Third Embodiment)

FIG. 16 is a schematic cross sectional lateral view of a thirdembodiment of image pickup device according to the invention and FIG. 17is an exploded schematic perspective view of the embodiment. In FIGS. 16and 17, the components that are same as or similar to those of the firstand second embodiments are denoted respectively by the same referencesymbols and will not be described any further.

In this embodiment, the input/output terminals 103 of the photoelectricconverter substrates 1 are arranged on surfaces different from the lightreceiving surfaces of the photoelectric converters 100 in order tofurther reduce the non-light receiving areas of the light receivingsurfaces. With this arrangement, almost all the surfaces of thephotoelectric converter substrates 1 operate as light receiving surfacesat a side thereof. Therefore, as a plurality of photoelectric convertersubstrates are arranged side by side, the light receiving pixels formedon the photoelectric converter substrates 1 are smoothly arrangedwithout any particularly large gaps to increase the effective area ofthe embodiment.

FIG. 17 is an exploded schematic perspective view of the image pickupdevice of FIG. 16. As shown in FIG. 17, a plurality of photoelectricconverter substrates 1 are bonded to a scintillator 3 by means ofadhesive 6 and the input/output terminals 103 of the photoelectricconverter substrates 1 are formed on respective surfaces that aredifferent from the light receiving surfaces of the photoelectricconverter substrates 1. Each of the photoelectric converter substrates 1is provided with etched holes 106, through which a leads are extendingfrom the side of the light receiving surface of the photoelectricconverter substrate 1 to the rear surface side. A base member 7 providedwith slits 70 corresponding to the leads of the photoelectric convertersubstrates 1 is arranged thereunder and provided with electrodes 700corresponding to the leads.

FIG. 18A is a schematic plan view of one of the photoelectric convertersubstrates 1 of the embodiment and FIG. 18B is a schematic crosssectional view corresponding to FIG. 18A.

Light receiving pixels (photoelectric converters) 100 are arrangedtwo-dimensionally on the silicon substrate 1. Additionally, drivecircuits 101, 102 for sequentially driving the two-dimensionallyarranged light receiving pixels and wires for connecting the circuits,the pixels and the electrode terminals are formed on the siliconsubstrate 1.

The light receiving pixels 100 are arranged almost on the entire surfaceof the photoelectric converter substrate 1 at a pitch of 100 μm. Thedrive circuits 101, 102 are arranged so as to separate pixels.

FIGS. 19A through 19D are schematic cross sectional lateral views of oneof the photoelectric converter substrates 1 of the embodiment, showingmanufacturing steps for taking out an input/output terminal 103 from therear surface of the photoelectric converter substrate 1.

(Step 1 Polishing of Rear Surface)

Firstly, as shown in FIG. 19A, the photoelectric converter substrate 1is held to a holding substrate typically by means of wax and polished atthe rear surface thereof by about 100 μm in order to curtail the timerequired for the etching process.

(Step 2 Formation of Etching Mask and Etching)

Then, as shown in FIG. 19B, Al electrode 107 is etched as correspondingto an input/output terminal 103. The etching operation proceeds, usingan SiO₂ film 108 that is an alkali-resistant material as silicon waferetching mask because the etching operation is conducted in a stronglyalkali solution.

Thereafter, only the rear surface where the etching operation isconducted is exposed and the photoelectric converter substrate 1 isimmersed into an aqueous solution of TMAH (tetramethyl hydroxide) heatedto 80° C. for about 2 hours to complete the etching operation while allthe remaining surfaces are covered by silicon rubber in order to fendoff the etching solutions trying to touch them. Since an SiO₂ film isformed on the electrode, the etching operation terminates at the SiO₂film 108 even if the photoelectric converter substrate is over-etched.

(Step 3 Formation of Insulating Layer and through Hole)

Subsequently, as shown in FIG. 19C, an insulating layer 109 is formed onthe etched surface in order to prevent any leakage of electricity to theelectrode because the etched surface is that of a silicon semiconductor.More specifically, a 0.2 μm thick SiO₂ film layer is formed by CVD,although the SiO₂ film may be replaced by a film layer of an organicmaterial such as polyimide so long as it can effectively prevent anyleakage of electricity from occurring.

Then, the insulating layer and the film of the alkali-resistant materialis removed so that the hole 106 formed by etching gets to the electrode107. More specifically, a mask is formed by using photoresist and thenthe through hole is produced by RIE.

(Step 4 Formation of Rear Surface Electrode)

Thereafter, as shown in FIG. 19D, the exposed electrode 107 is taken outto the rear surface of the photoelectric converter surface 1 to producea rear surface electrode 110 by forming an aluminum film and patterningthe formed aluminum film.

(Step 5 Bonding External Circuit Substrate)

Then, in Step 5 (not shown), the photoelectric converter substrates 1are arranged side by side on the base member 7. The base member 7 isformed by using a ceramic substrate, taking the thermal expansioncoefficient and the rigidity of the photoelectric converter substrates 1into consideration. The base member 7 carries thereon an A/D converter,electrodes to be connected to the respective input/output terminals ofthe photoelectric converter substrates and slits 70 for connecting thephotoelectric converter substrates 1 and the electrodes on the basemember 7 that are formed in advance. The base member 7 and thephotoelectric converter substrates 1 are arranged in such a way that theslits 70 and the corresponding electrodes of the photoelectric convertersubstrates 1 are aligned relative to each other and then bondedtogether. Then, the flexible circuit substrates are made to extendthrough the slits by way of leads and the input/output terminals and thecorresponding electrodes are connected to each other. The photoelectricconverter substrates are arranged with gaps of 80 μm, considering thepossible alignment errors and the pitch of arranging the pixels.

Silicone resin showing a high modulus of elasticity is used as adhesiveso that the photoelectric converter substrates may remain free fromstress. The rear surface electrodes 110 formed on the photoelectricconverter substrates 1 and the electrodes formed on the base member 7are connected respectively and the wires are protected by a sealingmaterial. In this step, electronic parts 71 including processingcircuits are also mounted on the device.

CMOS elements are preferably used for the photoelectric converters.

A complete radiation image pickup device can be formed by laying ascintillator 3 (gadolinium sulfide: GdS or cesium iodide: CsI) forshifting the wavelength of radiation on the light receiving surfaces.More specifically, a scintillator sheet prepared by sandwiching a sheetof GdS between a pair of PET (polyethyleneterephthalate) films andshaping the multilayer product is bonded to the photoelectric convertersubstrates 1 by means of light transmitting adhesive.

The reliability of the prepared radiation image pickup device can beimproved by using a radiation shielding member 9 such as a fiber plateof lead glass that transmits light and absorbs radiation between thescintillator layer 3 and the photoelectric converter substrates 1 inorder to prevent any leaked X-rays that are not absorbed by thescintillator layer 3 from entering the photoelectric convertersubstrates 1 to degrade the operation characteristics and produceoperation errors.

Additionally, as in the first embodiment, a light transmitting substratesuch as an optical fiber plate may be arranged between the scintillatorlayer and the light receiving surfaces of the photoelectric convertersto improve the efficiency of light detection.

(Fourth Embodiment)

FIG. 21 is a schematic perspective view of the fourth embodiment ofimage pickup device according to the invention and FIGS. 22A and 22B areschematic cross sectional views of the embodiment of FIG. 21. FIG. 22Ais a schematic longitudinal cross section view of the embodiment takenalong line 22A—22A in FIG. 21, whereas FIG. 22B is a schematictransversal cross sectional view of the embodiment taken along line22B—22B in FIG. 21.

In this embodiment, an electrode is made to run through eachphotoelectric converter substrate 1 and extend to the rear surface sidein order to draw the information detected by the photoelectric convertersubstrate 1 to the outside of the sensor by way of a cable. In FIG. 21,reference numeral 111 denotes a radiation image sensor. In FIGS. 22A and22B, there are shown a CMOS image pickup element substrate 1, which is asort of an image pickup element, a light receiving pixel section 100formed on the CMOS image pickup element substrate 1, a wiring circuitsection 112 formed on the CMOS image pickup element substrate 1, athrough electrode 40 connected to the wiring circuit section 112, an FOP2 for transmitting visible light, a scintillator 3 for convertingvisible light into an electromagnetic wave that can be detected by theCMOS image pickup element, adhesive 8 for rigidly holding andelectrically connecting the CMOS image pickup element substrate 1 to abase member 7, a case 113 and a cable 114 for drawing electric signalsto the outside. Anisotropic electrically conductive adhesive ispreferably used for the adhesive.

Now, the process of preparing the CMOS image pickup element substrate 1will be described by referring to FIGS. 23A through 23E, of which FIGS.23A and 23C through 23E are schematic cross sectional views of asemiconductor wafer and FIG. 23B is a schematic plan view of thesemiconductor wafer of FIG. 23A.

Firstly, as shown in FIGS. 23A and 23B, a light receiving pixel section91 a, a processing circuits including a drive circuit and an outputcircuit (not shown) and a wiring circuit 91 b are formed on asemiconductor wafer 91 by means of an ordinary semiconductor process.

Then, as shown in FIG. 23C, a hole 92 that is deep but does not runthrough the wiring circuit section 91 is formed in the latter typicallyby anisotropic etching and an insulating layer and an electricallyconductive layer connected to the wiring circuit section 91 b are formedon the inner surface of the deep hole. Subsequently, as shown in FIG.23D, the semiconductor wafer 91 is etched from the rear surface 93 untilthe electrically conductive layer connected to the wiring circuitsection 91 b is exposed to produce a through electrode 94.

Finally, as shown in FIG. 23E, the semiconductor wafer is diced topredetermined chip dimensions along the dicing lines 95 as indicated bychain lines in FIG. 23E.

A radiation image pickup device for dental applications obtained bymounting such CMOS image pickup elements is compact and shows a verysmall peripheral non-effective surface area if compared with a devicerealized by mounting conventional image pickup elements. Such imagepickup elements and peripheral circuit sections are arrenged on a singlesubstrate.

The prepared radiation image pickup device 200 can be used as radiationimage sensor 82 of a radiation image pickup system as shown in FIG. 24.With such a system, X-rays from an X-ray source 80 are made to strikethe dental X-ray image sensor 82 (X-ray image sensor 10) arranged behindthe teeth to be examined in the oral cavity after passing through theteeth 81 in a manner as described earlier. Then, as shown in FIG. 22A,the wavelength of the incident radiation is changed to that of visiblelight by the scintillator 3 and the obtained visible light is projectedonto the light receiving pixel section 100 of the CMOS image pickupelements by way of the FOP (fiber optical plate) 2. Then the visiblelight is converted into an electric signal by the peripheral circuitsection and transmitted to a control unit 83 by way of the throughelectrodes 40 and the cable 114. The signal is then subjected to A/Dconversion and processed to produce an image of the teeth in the controlunit 83, which is then displayed on a monitor display 84 or printed by aprinter 85. The obtained image is then used for dental care.

(Fifth Embodiment)

FIG. 25 is a schematic conceptual view of an image processing systemaccording to the invention. The system will be described hereparticularly in terms of X-rays. An X-ray image of the object istransmitted from a radiation image pickup device 400 to an imageprocessor 402, which processes the image for the purpose of emphasizingthe contrast and coloring. The processed image is then displayed on adisplay unit 401. X-rays may be emitted further from X-ray generator 403according to an instruction from the image processor 402 typically inorder to change the angle of shooting the object and produce anotherX-ray image. With such a system, it is possible to shoot a small areasuch as molars and show a moving image thereof.

1. A radiation image pickup device having a plurality of photoelectricconverters and a plurality of photoelectric converter substratescarrying respective terminals connected to said photoelectric converterson light receiving surfaces of the photoelectric converter substrates,said device further comprising: leads connected to the terminals andextending to a side opposite to the light receiving surfaces of thephotoelectric converter substrates through gaps between the substrates;and a wavelength converter for wavelength-converting radiation and alight guide section for guiding light from said wavelength converter tosaid plurality of photoelectric converters, said wavelength converterand said light guide section being provided with the plurality ofphotoelectric converter substrates.